1. Field of the Invention
This invention relates to a laser device, and particularly to a minilaser device with both laser and frequency-doubling effects using NYAB [Nd.sub.x Y.sub.1-x Al.sub.3 (BO.sub.3).sub.4 (x=0.03-0.08)] single crystal as laser crystal.
2. Description of Related Art
With the development of laser technology and applications thereof, there is increasing demand for multifunction materials with both laser and non-linear optical effects so that the great interest has been aroused in investigation on the crystal materials and their laser devices which are capable of emitting visible laser light directly.
Prior to the 1970's, there were reports on scientific research work in obtaining multifunction crystals by means with doping LiNbO.sub.3 crystal with Tm.sup.3+ and Nd.sup.3+ ions. Experiments of self-frequency doubling lasers have been carried out with the crystal of Nd.sup.3+ : LiNbO.sub.3. It is found that owing to the doping of the unmatched valence and ionic radius of Nd.sup.3+ ions, the optical homegeneity of the crystal deteriorates such that it has not yet come into practical use. In 1983, Soviet scientists successfully developed the multifunction crystal of Nd.sub.0.2 Y.sub.0.8 Al.sub.3 (BO.sub.3).sub.4 to realize the self-frequency-doubling laser effect from 1.32 .mu.m to 0.66 .mu.m. Since 1986, The crystal of Nd.sub.x Y.sub.1-x Al.sub.3 (BO.sub.3).sub.4 (x=0.05-0.15) has been grown by flux method in the Institute of Crystal Material in Shandong University, with which the operation of self-frequency-doubling laser emissions from 1.06 .mu.m into 0.53 .mu.m has been realized at the pumping of a 587.8 nm laser beam of a pulsed dye laser. However, it is valueless to use a laser as a pumping source, which is itself capable of tuning to a wavelength of 0.53 .mu.m with higher energy output, to generate the 0.53 .mu.m laser beam with lower energy output by the self-frequency-doubling effect. The inventors have found, by an investigation of the relationship between the structure and the properties of the material, the crystal of Nd.sub.x Y.sub.1-x Al.sub.3 (BO.sub.3).sub.4 is an ideal self-frequency-doubling laser material because of its large binding energy, high hardness and high thermal conductivity, and of good physico-chemical stability. The optical homogeneity of the crystal has not been deteriorated by the doping of Nd.sup.3+ ions. On the other hand, it has lower concentration quenching effect when doping the crystal with a high Nd.sup.3+ level which is necessary for a minilaser device with high gain coefficient.
Due to the special conditions required in the experiment of self-frequency-doubling laser, in order to study the relationship between the frequency-doubling effect and length of the crystal bars as well as the Nd.sup.3+ doping level, the inventors have modified the non-linear optical couple equation to determine the range of numerical value of X, to be X=0.03-0.08.
In a general sense the object of the invention is to provide a practical minilaser device with both laser and frequency-doubling effects utilizing the single crystal of Nd.sub.x Y.sub.1-x Al.sub.3 (BO.sub.3).sub.4 (x=0.03-0.08), with the output laser wavelength at 0.532 .mu.m.